Doctors could be misdiagnosing thousands of elderly people with dementia because they are confusing the condition with the side-effects of many common medicines.

A study carried out by researchers in the US suggests that many day-to-day drugs such as common prescription medication and pills sold by pharmacists can have side-effects similar to symptoms of dementia.

They say drugs used to treat allergies, depression, migraine and irritable bowel syndrome can produce dementia-like side effects.

These include signs of confusion, memory loss, disorientation and blurred vision.

Some side-effects can be mistaken for the effects of old age and age-related illness

Dr Jacobo Mintzer, University of South Carolina

They can also take the form of patients licking their lips before they begin to speak, or falling for no obvious reason or increased anxiety and rapid breathing.

Elderly people are most at risk of experiencing these side-effects because many are on a number of different medications for a variety of conditions.

Their bodies are also less efficient which means that the drugs stay in their bodies longer.

The US doctors believe that many doctors are failing to take these side-effects into account when treating elderly patients.

Elderly people traditionally take more prescription drugs and over the counter remedies than the rest of the population.

In the UK, elderly people account for 18% of the population but they consume 45% of all prescription drugs.

The US research suggests that elderly people living in nursing homes are most at risk of receiving the wrong treatments because they take even more prescription medicines that those living at home.

A recent study reported that 97% of elderly people in nursing homes were taking prescription drugs compared with 71% of those living in the community.

Better understanding

Dr Jacobo Mintzer, of the Medical University of South Carolina, said the study "highlights the need for better understanding, assessment and management" of side-effects in elderly people.

He said doctors needed to be aware that symptoms that may look like signs of dementia could be something else.

"Some side-effects can be mistaken for the effects of old age and age-related illness.

"Physicians should be alert to the possibility that dry mouth constipation and blurred vision may be caused by medication.

"Changes in intellectual function should also be investigated, particularly in patients who already have cognitive impairment," he said.

Dr Mintzer said the range and severity of side-effects to everyday drugs among elderly people may be underestimated.

"There is little published information on the complex combinations of drugs used in elderly people," he said.

He said doctors should ensure that where possible elderly patients are prescribed drugs that have few side-effects.

Writing in the latest issue of the Journal of the Royal Society of Medicine, Dr Mintzer added that patients and their carers should be told of possible side-effects at all times during their treatment.

A spokeswoman for Age Concern welcomed the study.

"Many side-effects, such as dizziness, blurred vision, increased anxiety and
falls without obvious reason, tend to be mistaken for symptoms of old-age," she said.